Steroid treatment of anterior uveitus is effective but frequently associated with cataract formation after prolonged use. Development of an effective substitute for steroids, free of these safety concerns, would be a substantial advance. In a Phase I SBIR, we proposed a novel therapeutic candidate for treatment of uveitus, based on the introduction of a proprietary novel inhibitor of the inducible nitric oxide (NO) synthase (iNOS), an enzyme whose de novo upregulated expression accounts for the release of injurious quantities of NO and produces inflammatory injury in uveitis. Our development candidate, GED (guanidinoethyldisulfide), selectively inhibits iNOS activity and scavenges peroxynitrate, a toxic oxidant formed from the reaction of NO and superoxide. In a rat model of endotoxin-induced uveitis (EIU), GED proved highly effective when administered either systemically of topically (as an 0.3% ophthalmac solution). We also carried out studies that suggest that GED therapy is safe, as evidenced by negative in vitro and in vivo genotoxicology assays, a NOEL in rats and dogs for systemic GED administration 100-fold greater than the potential absorbed drug from ophthlamic use, a lack of cytotoxicity in cultured epithelial cells, and absenceof ocular injury in rabbits challenged with a supratherapeutic (10%) GED ophthalmic solution. In the current Phase 2 SBIR, we will conduct safety and efficacy studies in order to move GED forward to the stage where human clinical testing can begin. To this end, we will first test GED in rabbits to establish the therapeutic window of opportunity in a classic model of uveitis and we will test the safety of the compound in 60 day and 6 month repeat dose studies. The latter study will be critical to establish that GED, in contrast to steroids, does not induce cataract formation. The results of the studies proposed in the current Phase III SBIR application will provide the basis for an FDA-approved IND to perform Phase I/II clinical trials.